Portland >> The western monarch butterfly population is the lowest it has been in five years.

That is according to estimates from last year’s Western Monarch Thanksgiving Count, an annual monarch census facilitated by the Xerces Society for Invertebrate Conservation. Over 150 citizen scientists participated in the 2017 count, and were able to cover more sites than ever before.

“I think people in California, and throughout the U.S., have understood that monarchs are in trouble and really want to help,” said Sarina Jepsen, the Xerces Society endangered species program director. “Unfortunately, despite this massive search effort we’ve had, we’re not counting any more butterflies.”

Volunteers reported seeing just over 192,000 monarchs across 262 sites in the western states. To put that number in perspective, back in 2013, the count totaled 211,000 butterflies — but about 100 fewer sites were surveyed. This indicates the western monarch population continues to shrink even as conservationists strive to restore their habitat, said Jepson.

“In the western U.S., there are efforts throughout the landscape to restore breeding habitat by planting milkweed and nectar plants for monarchs,” she said. Particular attention has been paid to overwintering sites along the California coast, where monarchs live between November and March. Over the last few decades, monarchs have disappeared from about 60 California overwintering sites.

Housing developments now stand where the coastline once teemed with butterflies. “Along the California coast, these areas where these monarchs choose to spend winter are the same places that people really like to live,” explained Jepson. Though habitat loss is a huge factor in the western monarch’s decline, researchers aren’t sure it’s their biggest threat.

Eastern monarchs have also dwindled in recent decades. Their decline was driven by changes in agriculture, namely the introduction of GMO corn and soy products and the increased use of certain herbicides, said Jepson.

“The story in the western U.S., with our smaller coastal California population, is less clear,” she said.

The western monarch faces many threats as it flutters through California. Changes in the use of agricultural land and herbicides have paralleled shifts in the East, to an extent. The quality of monarch habitat pales in comparison to past conditions as milkweed, flowering plants and trees for clustering become more scarce. Climate change, severe droughts and intense winter storms have left their mark on overwintering sites. Disease, wildfires, smoke and mudslides may have a part to play, but it’s not well understood, Jepson said.

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At a few sites in Santa Cruz County, including Natural Bridges State Park and Moran Lake, the number of monarchs was maintained or improved. At Lighthouse Field State Park, where clustering trees are currently being restored, the butterfly count was also stable. Pismo Beach remains an important overwintering site, though the 12,000 monarchs spotted last year signal quite a drop from the 100,000 counted back in 1997.

At Pacific Grove’s Monarch Sanctuary there were 17,100 counted in 2016. That dropped to 7,350 in 2017.

Monarchs are classified as a “Species of Greatest Conservation Need” by the state, but they and their overwintering habitat enjoy little legislative protection. After assessing the current ordinances in place to protect the butterflies, the Xerces Society “concluded there was essentially no protection,” said Jepson. The few city- and county-specific regulations that do exist are limited in scope, only protecting monarch habitat when the insects are actually present.

As many monarch hotspots are public areas, the habitat is often degraded by ordinary maintenance and use of the space.

U.S. Fish and Wildlife Service are currently assessing whether monarchs should be added to the endangered species list. They are bound to announce their decision by June 2019.

People who have lived in California for many decades are noticing the gradual disappearance of their favorite iconic insect, said Jepson. As recently as the 1980s, western monarchs numbered in the millions. Jepson first saw them in the 1996 at Natural Bridges State Beach in Santa Cruz, when numbers were still over 1.2 million. The Thanksgiving Count was founded a year later.

“It’s interesting when we see a population of animals go from being so numerous to so few,” she said. “I think that many people recognize that this butterfly should be able to exist with humans in the landscape - They really enrich our lives.”